Cache responses

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.3.1
+FROM ruby:2.4.0
 
 RUN mkdir /app
 WORKDIR /app
@@ -6,4 +6,4 @@ ADD Gemfile /app/Gemfile
 ADD Gemfile.lock /app/Gemfile.lock
 RUN bundle install --without development test
 ADD . /app
-CMD ./wait-for-it.sh db:5432 -- unicorn -c /app/config/unicorn.rb
+CMD ./wait-for-it.sh db:5432 -s -- wait-for-it.sh memcache:11211 -s -- unicorn -c /app/config/unicorn.rb

Gemfile

@@ -4,7 +4,9 @@ source 'http://rubygems.org'
 
 ruby '2.4.0'
 
+gem 'dalli'
 gem 'fixer'
+gem 'kgio'
 gem 'newrelic_rpm'
 gem 'oj'
 gem 'rack-cors'

Gemfile.lock

@@ -4,6 +4,7 @@ GEM
     ansi (1.5.0)
     ast (2.3.0)
     coderay (1.1.1)
+    dalli (2.7.6)
     fixer (0.6.0)
       oga (~> 2.0)
     kgio (2.10.0)
@@ -64,7 +65,9 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  dalli
   fixer
+  kgio
   minitest
   minitest-around
   newrelic_rpm

config/app.rb

@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 
+require 'dalli'
 require 'pathname'
 
 # Encapsulates app configuration
 module App
   class << self
-    attr_reader :version, :released_at
+    attr_reader :cache, :version, :released_at
 
     def env
       ENV['RACK_ENV'] || 'development'
@@ -16,6 +17,7 @@ module App
     end
   end
 
-  @version = `git rev-parse --short HEAD 2>/dev/null`.strip!
+  @cache = Dalli::Client.new
   @released_at = `git show -s --format=%ci HEAD`
+  @version = `git rev-parse --short HEAD 2>/dev/null`.strip!
 end

docker-compose.yml

@@ -2,6 +2,8 @@ version: '2'
 services:
   db:
     image: postgres
+  memcache:
+    image: memcached
   web:
     build: .
     volumes:
@@ -9,7 +11,9 @@ services:
     ports:
       - 8080:8080
     environment:
-      - RACK_ENV=production
-      - DATABASE_URL=postgres://postgres@db/postgres
-    depends_on:
+      RACK_ENV: production
+      DATABASE_URL: postgres://postgres@db/postgres
+      MEMCACHE_SERVERS: memcache
+    links:
       - db
+      - memcache

lib/api.rb

@@ -5,6 +5,8 @@ require 'sinatra'
 require 'rack/cors'
 require 'quote'
 
+set :cache_ttl, 900 # 15 minutes
+
 configure :development do
   set :show_exceptions, :after_handler
 end
@@ -50,6 +52,12 @@ helpers do
   def encode_json(data)
     Oj.dump(data, mode: :compat)
   end
+
+  def cache
+    App.cache.fetch request.fullpath, settings.cache_ttl do
+      yield
+    end
+  end
 end
 
 use Rack::Cors do
@@ -69,13 +77,17 @@ get '/' do
 end
 
 get '/latest' do
-  last_modified quote_attributes[:date]
-  jsonp quote_attributes
+  cache do
+    last_modified quote_attributes[:date]
+    jsonp quote_attributes
+  end
 end
 
 get(/(?<date>\d{4}-\d{2}-\d{2})/) do
-  last_modified quote_attributes[:date]
-  jsonp quote_attributes
+  cache do
+    last_modified quote_attributes[:date]
+    jsonp quote_attributes
+  end
 end
 
 not_found do

spec/api_spec.rb

@@ -11,6 +11,10 @@ describe 'the API' do
   let(:json) { Oj.load(last_response.body) }
   let(:headers) { last_response.headers }
 
+  before do
+    App.cache.flush
+  end
+
   it 'describes itself' do
     get '/'
     last_response.must_be :ok?
@@ -86,4 +90,10 @@ describe 'the API' do
     get '/latest?from=GBP&to=USD&amount=100'
     json['rates']['USD'].must_be :>, 100
   end
+
+  it 'caches quotes' do
+    App.cache.set '/latest', 'foo'
+    get '/latest'
+    last_response.body.must_equal 'foo'
+  end
 end

spec/edge_cases_spec.rb

@@ -10,6 +10,10 @@ describe 'the API' do
   let(:app)  { Sinatra::Application }
   let(:json) { Oj.load(last_response.body) }
 
+  before do
+    App.cache.flush
+  end
+
   it 'handles unfound pages' do
     get '/foo'
     last_response.status.must_equal 404